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What they don't mention is how efficient the solar cells produced are. NASA's NIAC studied making solar cells in a similar manner and estimated they could produ

by gene-h 4y ago

What they don't mention is how efficient the solar cells produced are. NASA's NIAC studied making solar cells in a similar manner and estimated they could produce solar cells with 6-9% efficiency[0]. Efficiency was limited due to impurities in the silicon they produced. They have made some pretty big improvements over the NIAC work by being able to produce cover glass, which the NIAC study didn't even consider. Another big question is how much mass needs to be shipped up from earth to manufacturer solar cells. Dopants will still need to be shipped up as they cannot currently be obtained with this method, but the mass per area solar cell is practically nothing. More concerning are the electrodes for their electrolysis cell. They are literally electrolyzing molten lava. Molten silicates are a very good solvent and the hot oxidizing environment of the anode is quite harsh. We do have materials which can withstand this environment, but how long will they last? How much power can the whole set up produce and would it be more than landing the setup's weight in solar cells? Regardless this is still a major advance. Materials processing of this level suitable for the lunar environment has not been previously demonstrated. [0]https://www.niac.usra.edu/files/library/meetings/annual/jun00/433Ignatiev.pdf https://www.niac.usra.edu/files/library/meetings/annual/jun0...

dotnet00 4y ago
They claim to achieve 99.999% purity on the silicon, so it sounds like they might do better than 6-9% on efficiency. But then again if they were anywhere near Earth produced panels, they would probably be saying that to everyone who would listen.
- addaon 4y ago
  Nine nines is the usual target for semiconductor work… five nines is off-the-shelf. It’s impressive for “on the moon,” but I’d expect a significant performance shortfall from what we’re used to.
  - sacred_numbers 4y ago
    Surprisingly it appears not to be too far off standard solar panel efficiencies. According to this source[0], five nines silicon (5N) is called Upgraded Mettalurgical-grade (UMG) silicon. According to this paper[1], efficiencies over 20% have been reached with UMG silicon. [0]http://www.greenrhinoenergy.com/solar/technologies/pv_manufacturing.php http://www.greenrhinoenergy.com/solar/technologies/pv_manufa... [1]https://www.sciencedirect.com/science/article/abs/pii/S0038092X21002711#:~:text=20.76%25%20record%20efficiency https://www.sciencedirect.com/science/article/abs/pii/S00380....
  - tomrod 4y ago
    I mean, how many of these do you need to produce as a seed? You certainly don't start the process at full capacity; if there are ways this nests into an evolving, self-reinforcing system to prepare for human contact then it's a fantastic start. It's not like we have huge space constraints for small starts, I reckon?
  - lightedman 4y ago
    99.999% is what we used in our 156.25mm x 156.25mm polycrystalline cells when I did solar manufacturing. 21% efficiency was easily obtained, allowing ~300w in a 60-cell panel.
  - rippercushions 4y ago
    However, there's no atmosphere or weather to worry about on the moon, so I'd expect that to improve efficiency quite a bit compared to the Earth. The real challenge with solar power on the Moon remains the two-week day/night cycle, which means either massive batteries (impractical) or awkward polar cliff locations to minimize the hit.
    - freeone3000 4y ago
      Or a (partial) ring around the equator, video game style.
    - mLuby 4y ago
      There is a thin "atmospheric" layer of molecules floating around the lunar surface. Indistinguishable from vacuum for most purposes but it might affect that many 9's of purity. https://www.nasa.gov/mission_pages/LADEE/news/lunar-atmosphere.html https://www.nasa.gov/mission_pages/LADEE/news/lunar-atmosphe...
  - deleted 4y ago
    [deleted]
ricardobeat 4y ago
Isn’t solar exposure on the moon stronger than earth due to the lack of an atmosphere? Efficiency per sqm might end up being higher.
- beakergordon 4y ago
  I think the implied comparison was: do we launch panels to the moon or build them in-situ? The increased solar exposure should boost both of these cases by the same percentage, but if the Earth-manufactured panel is (e.g.) 3x as efficient, it might still make more sense to ship them.
- dr_orpheus 4y ago
  Yep, you get about 36% more sun above the atmosphere. 1361 W/m^2 above the atmosphere vs ~1000 W/m^2 on a clear day [0]. Now you just need to bring big enough batteries to survive 14 days in a row with no sun. [0] https://en.wikipedia.org/wiki/Solar_irradiance#Irradiance_on_Earth's_surface https://en.wikipedia.org/wiki/Solar_irradiance#Irradiance_on...
  - leidenfrost 4y ago
    Considering the fact that you have the entire moon as available surface, you'd rather lift a giant rock with that power and store all the potential gravitational energy as a "battery". A 10 ton rock, lifted up to 50m high, will store up to 810M Joules at moon gravity
    - deleted 4y ago
      [deleted]
    - sbierwagen 4y ago
      >A 10 ton rock, lifted up to 50m high, will store up to 810M Joules at moon gravity Wrong prefix? I think you meant 810K Joules. For Earth gravity: 10,000 kg times 9.8 m/s^2 times 50 m = 4.9 megajoules, 1.36 kilowatthours. (Anker sells a 2.04 KWh battery pack for US$1999: https://www.anker.com/products/a1780 https://www.anker.com/products/a1780 The manual says it masses 30.5 kg, so that's a cool 491.88x difference in mass power density.) Again, that's for Earth gravity. Lunar gravity: 10,000 kg times 1.62 m/s^2 times 50 m = 0.81 megajoules, 0.225 kilowatthours. (2,976x difference in mass power density vs the lithium battery.) Gravity storage isn't economical on Earth, and it's really not economical on the Moon, where gravity is lighter.
jmyeet 4y ago
> What they don't mention is how efficient the solar cells produced are. This... may or may not matter. When it comes to solar power on the Moon, there are significant advantages and some serious disadvantages. The most obvious advantage is that there is no weather and no atmosphere. This means a lunar solar cell has way more potential power generation than an terrestrial solar cell. The big disadvantage is the long day night cycle. The Moon is tidally locked with Earth with an orbit of 28 days so that's basically 14 days of day and 14 days of night. You have to work around this problem with batteries, which add a ton more mass, having panels (and settlements most likely) at the poles or running a network of solar cells around the Moon with power cables. Settling the poles makes sense as this is where the most water is. But having a network of panels probably makes a lot of sense too. For one, aluminium is abundant so making electrical cables should be entirely possible. > Another big question is how much mass needs to be shipped up from earth to manufacturer solar cells. Yes, this is a huge factor, probably way more than efficiency is. Or at least we should look at power generation per unit mass shipped from EArth.
- super5000 4y ago
  If they're going to make solar panels on the moon, perhaps the creativity won't stop there: Maybe we don't need to ship batteries, either. They can make batteries out of moon rocks [1], use fly wheels, melt lava, etc. None super efficiently, but as a start. [1] https://en.wikipedia.org/wiki/Gravity_battery https://en.wikipedia.org/wiki/Gravity_battery
- narag 4y ago
  You have to work around this problem with batteries... It's only a problem if you want to use the energy for systems that must be always available. If you intend to use it to power a factory, let's say to make more panels, you just operate 50% of time that, without clouds or any atmosphere filter, is actually better than on Earth. For continuous support, take a nuclear reactor or build a wired net near a pole so when night comes to one station, you receive power from another.
mlyle 4y ago
> We do have materials which can withstand this environment, but how long will they last? How much power can the whole set up produce and would it be more than landing the setup's weight in solar cells? Oh, of course this is terrible now. It would have a very, very large required scale to come out ahead compared to just shipping power or power generation some other way (if this is true at any scale). It is also surely not fully baked yet. On the other hand... it's a notable step towards being able to build "big" in space and might be worth doing to learn more about the practical aspect even if it's higher risk and more costly than shipping a bunch of PV. The bigger problem is how practical is it to use PV at all on much of the moon.
- schiffern 4y ago
  >The bigger problem is how practical is it to use PV at all on much of the moon. I think part of the solution will involve using "regular stuff" (which can be sourced from lunar atoms) like batteries. Don't use lithium batteries to continuously power an oxygen generator. Instead, have an enlarged oxygen generator and store half the flow for use at night. Don't use lithium batteries to power a heater at night, instead "pre-charge" heat in a dirt thermal mass during the day. Don't use lithium batteries to power a continuous CO2 scrubber, instead use a liquid amine scrubber and recharge the fluid tanks during the day. Etc etc Obviously you need to do in-depth tradeoff math for each case, but my napkins say "the system is the battery" wins in many cases.
  - paranoidrobot 4y ago
    Lunar night being about 14 days might make that a bit more difficult for any permanent settlement. Storing 14+ days worth of <everything> is going to mean massive amounts of storage.
    - mlyle 4y ago
      Yup. Nuclear seems likely to be part of the solution.
    - schiffern 4y ago
SECProto 4y ago
> Another big question is how much mass needs to be shipped up from earth to manufacturer solar cells. If you take the linked page at face value, it explicitly states: > without special substances brought from Earth. (I suspect, like most press releases, some important details aren't being provided. Maybe dopants aren't considered "special substances")
- gene-h 4y ago
  This study[0] estimated that less than a microgram of dopant is needed per m^2 and that producing 5 MW of solar cells requires 1 gram of phosphorous. [0]https://ascelibrary.org/doi/abs/10.1061/(ASCE)0893-1321(2001)14:2(77) https://ascelibrary.org/doi/abs/10.1061/(ASCE)0893-1321(2001...
deleted 4y ago
[deleted]
otikik 4y ago
The Earth's atmosphere absorbs and reflects solar energy - only 48% of the solar energy reaches the surface of the planet[1]. I didn't see any mention of this on the link you provided, I don't know if that 6-9% figure includes this. If it's not included, then the extra energy available could raise the output to an equivalent of a 12-18% efficiency cell on Earth's surface, wouldn't it? [1] https://earthobservatory.nasa.gov/features/EnergyBalance/page4.php https://earthobservatory.nasa.gov/features/EnergyBalance/pag...

by gene-h 4y ago

dotnet00 4y ago

They claim to achieve 99.999% purity on the silicon, so it sounds like they might do better than 6-9% on efficiency. But then again if they were anywhere near Earth produced panels, they would probably be saying that to everyone who would listen.

addaon 4y ago
Nine nines is the usual target for semiconductor work… five nines is off-the-shelf. It’s impressive for “on the moon,” but I’d expect a significant performance shortfall from what we’re used to.
- sacred_numbers 4y ago
  Surprisingly it appears not to be too far off standard solar panel efficiencies. According to this source[0], five nines silicon (5N) is called Upgraded Mettalurgical-grade (UMG) silicon. According to this paper[1], efficiencies over 20% have been reached with UMG silicon. [0]http://www.greenrhinoenergy.com/solar/technologies/pv_manufacturing.php http://www.greenrhinoenergy.com/solar/technologies/pv_manufa... [1]https://www.sciencedirect.com/science/article/abs/pii/S0038092X21002711#:~:text=20.76%25%20record%20efficiency https://www.sciencedirect.com/science/article/abs/pii/S00380....
- tomrod 4y ago
  I mean, how many of these do you need to produce as a seed? You certainly don't start the process at full capacity; if there are ways this nests into an evolving, self-reinforcing system to prepare for human contact then it's a fantastic start. It's not like we have huge space constraints for small starts, I reckon?
- lightedman 4y ago
  99.999% is what we used in our 156.25mm x 156.25mm polycrystalline cells when I did solar manufacturing. 21% efficiency was easily obtained, allowing ~300w in a 60-cell panel.
- rippercushions 4y ago
  However, there's no atmosphere or weather to worry about on the moon, so I'd expect that to improve efficiency quite a bit compared to the Earth. The real challenge with solar power on the Moon remains the two-week day/night cycle, which means either massive batteries (impractical) or awkward polar cliff locations to minimize the hit.
  - freeone3000 4y ago
    Or a (partial) ring around the equator, video game style.
  - mLuby 4y ago
    There is a thin "atmospheric" layer of molecules floating around the lunar surface. Indistinguishable from vacuum for most purposes but it might affect that many 9's of purity. https://www.nasa.gov/mission_pages/LADEE/news/lunar-atmosphere.html https://www.nasa.gov/mission_pages/LADEE/news/lunar-atmosphe...
- deleted 4y ago
  [deleted]

ricardobeat 4y ago

Isn’t solar exposure on the moon stronger than earth due to the lack of an atmosphere? Efficiency per sqm might end up being higher.

beakergordon 4y ago
I think the implied comparison was: do we launch panels to the moon or build them in-situ? The increased solar exposure should boost both of these cases by the same percentage, but if the Earth-manufactured panel is (e.g.) 3x as efficient, it might still make more sense to ship them.
dr_orpheus 4y ago
Yep, you get about 36% more sun above the atmosphere. 1361 W/m^2 above the atmosphere vs ~1000 W/m^2 on a clear day [0]. Now you just need to bring big enough batteries to survive 14 days in a row with no sun. [0] https://en.wikipedia.org/wiki/Solar_irradiance#Irradiance_on_Earth's_surface https://en.wikipedia.org/wiki/Solar_irradiance#Irradiance_on...
- leidenfrost 4y ago
  Considering the fact that you have the entire moon as available surface, you'd rather lift a giant rock with that power and store all the potential gravitational energy as a "battery". A 10 ton rock, lifted up to 50m high, will store up to 810M Joules at moon gravity
  - deleted 4y ago
    [deleted]
  - sbierwagen 4y ago
    >A 10 ton rock, lifted up to 50m high, will store up to 810M Joules at moon gravity Wrong prefix? I think you meant 810K Joules. For Earth gravity: 10,000 kg times 9.8 m/s^2 times 50 m = 4.9 megajoules, 1.36 kilowatthours. (Anker sells a 2.04 KWh battery pack for US$1999: https://www.anker.com/products/a1780 https://www.anker.com/products/a1780 The manual says it masses 30.5 kg, so that's a cool 491.88x difference in mass power density.) Again, that's for Earth gravity. Lunar gravity: 10,000 kg times 1.62 m/s^2 times 50 m = 0.81 megajoules, 0.225 kilowatthours. (2,976x difference in mass power density vs the lithium battery.) Gravity storage isn't economical on Earth, and it's really not economical on the Moon, where gravity is lighter.

jmyeet 4y ago

> What they don't mention is how efficient the solar cells produced are. This... may or may not matter. When it comes to solar power on the Moon, there are significant advantages and some serious disadvantages. The most obvious advantage is that there is no weather and no atmosphere. This means a lunar solar cell has way more potential power generation than an terrestrial solar cell. The big disadvantage is the long day night cycle. The Moon is tidally locked with Earth with an orbit of 28 days so that's basically 14 days of day and 14 days of night. You have to work around this problem with batteries, which add a ton more mass, having panels (and settlements most likely) at the poles or running a network of solar cells around the Moon with power cables. Settling the poles makes sense as this is where the most water is. But having a network of panels probably makes a lot of sense too. For one, aluminium is abundant so making electrical cables should be entirely possible. > Another big question is how much mass needs to be shipped up from earth to manufacturer solar cells. Yes, this is a huge factor, probably way more than efficiency is. Or at least we should look at power generation per unit mass shipped from EArth.

super5000 4y ago
If they're going to make solar panels on the moon, perhaps the creativity won't stop there: Maybe we don't need to ship batteries, either. They can make batteries out of moon rocks [1], use fly wheels, melt lava, etc. None super efficiently, but as a start. [1] https://en.wikipedia.org/wiki/Gravity_battery https://en.wikipedia.org/wiki/Gravity_battery
narag 4y ago
You have to work around this problem with batteries... It's only a problem if you want to use the energy for systems that must be always available. If you intend to use it to power a factory, let's say to make more panels, you just operate 50% of time that, without clouds or any atmosphere filter, is actually better than on Earth. For continuous support, take a nuclear reactor or build a wired net near a pole so when night comes to one station, you receive power from another.

mlyle 4y ago

> We do have materials which can withstand this environment, but how long will they last? How much power can the whole set up produce and would it be more than landing the setup's weight in solar cells? Oh, of course this is terrible now. It would have a very, very large required scale to come out ahead compared to just shipping power or power generation some other way (if this is true at any scale). It is also surely not fully baked yet. On the other hand... it's a notable step towards being able to build "big" in space and might be worth doing to learn more about the practical aspect even if it's higher risk and more costly than shipping a bunch of PV. The bigger problem is how practical is it to use PV at all on much of the moon.

schiffern 4y ago
>The bigger problem is how practical is it to use PV at all on much of the moon. I think part of the solution will involve using "regular stuff" (which can be sourced from lunar atoms) like batteries. Don't use lithium batteries to continuously power an oxygen generator. Instead, have an enlarged oxygen generator and store half the flow for use at night. Don't use lithium batteries to power a heater at night, instead "pre-charge" heat in a dirt thermal mass during the day. Don't use lithium batteries to power a continuous CO2 scrubber, instead use a liquid amine scrubber and recharge the fluid tanks during the day. Etc etc Obviously you need to do in-depth tradeoff math for each case, but my napkins say "the system is the battery" wins in many cases.
- paranoidrobot 4y ago
  Lunar night being about 14 days might make that a bit more difficult for any permanent settlement. Storing 14+ days worth of <everything> is going to mean massive amounts of storage.
  - mlyle 4y ago
    Yup. Nuclear seems likely to be part of the solution.
  - schiffern 4y ago

SECProto 4y ago

> Another big question is how much mass needs to be shipped up from earth to manufacturer solar cells. If you take the linked page at face value, it explicitly states: > without special substances brought from Earth. (I suspect, like most press releases, some important details aren't being provided. Maybe dopants aren't considered "special substances")

gene-h 4y ago
This study[0] estimated that less than a microgram of dopant is needed per m^2 and that producing 5 MW of solar cells requires 1 gram of phosphorous. [0]https://ascelibrary.org/doi/abs/10.1061/(ASCE)0893-1321(2001)14:2(77) https://ascelibrary.org/doi/abs/10.1061/(ASCE)0893-1321(2001...

deleted 4y ago

[deleted]

otikik 4y ago

The Earth's atmosphere absorbs and reflects solar energy - only 48% of the solar energy reaches the surface of the planet[1]. I didn't see any mention of this on the link you provided, I don't know if that 6-9% figure includes this. If it's not included, then the extra energy available could raise the output to an equivalent of a 12-18% efficiency cell on Earth's surface, wouldn't it? [1] https://earthobservatory.nasa.gov/features/EnergyBalance/page4.php https://earthobservatory.nasa.gov/features/EnergyBalance/pag...